Okay, so here's my idea for Ridley.
Size-wise, Ridley borrows a bit from his Other M "adolescent" form in terms of basic body structure and size, crawling on all-fours like a lizard and staying low off the ground. His tail is curled up like a scorpion's ready to strike, and his wings, while on the ground, are shrunken and folded up. He's slow and long, but also is always crouching, meaning he can dodge some high attacks, but overall he's not a decent character when on the ground and has weak jumps/recovery. He's also a light-weight heavy, around Charizard.
He attacks with bites, claws slashing, and occasionally his tail. A fast character who can rack up damage, but he's got weak knock-back overall and his attacks hit low and can be jumped over. His Grab has him using his tail as a hookshot-like object, grabbing the foe and pulling them in, which he can then unleash powerful throws.
The game-changer of Ridley is his Up-B, "Devil Wings", which is like Pit's Wings of Icarus move, although Ridley is much more agile when flying around and easier to steer, although he's a larger target. Ridley's flight-time is COMPOUNDED, meaning it doesn't recover when he lands...instead it will continue to decrease as you fly till his wings disappear, and he won't grow them back for a decent amount of time. So you can't spam Devil Wings the whole battle. This is to "balance" Ridley out as, when he's flying, he can utilize stronger versions of his Special Moves.
Neutral Special is Flare Barrage, where he shoots out five fireballs successively in a straight line if you hold B. When Flying, Ridley instead shoots out a giant fireball diagonally downward that's far more powerful.
Side Special is Scorpion Strike, where he charges up and then shoots his tail forward like a spear to pierce foes and can be used to tether recovery. When used while Flying, Ridley shoots his tail downward, strikes a foe, and then pulls them up and tosses them skyward.
Down Special is Nail Scrape, Ridley jumps forward a bit and, if he lands on a foe, he'll scrape them along the ground with his claws and then throw them (like the move he used on Samus in the SSE cutscene). When used while jumping, he instead slams them down right into the ground. When Flying, Ridley swoops down and slashes his claws in a downward arc, possibly Meteor Smashing foes below.
So, my idea with Ridley is that his Flying Abilities are VERY strong...but highly limited as he can't use Devil Wings that long as they fizzle out quickly and must recharge. And without his wings, Ridley can barely jump and has a hard time moving around the stage. So players must seek a balance, only utilizing Devil Wings during the best and most opportunistic situations. Or else they're left with a lanky, purple lizard who is slow as molasses.